Cathode.



HENRY STAFFORD Specification of Letters Patent. I

HATFIELD, OF BRIGHTON, ENGLAND.

CATHODE.

Patented J'uly23, 1907.

Appliiation filed AngustZO, I906. Serial llo. 331,398.

To all whom it may concern: 4

Be it known that I, HENRY Srassonn HATFIELD, a subject of the King'oiGreat Britain and Ireland, residing at LewisRoad, Brighton, in thecounty of S ussex",

England, have invented new and useful Improvements in Cathodes, of whichthe following isa specification.

My invention relatesto improvements in cathodes for electrolyticpurposes specially applicable for use with electrolytes containingmercuric salts in solution. 'It is usual to employ cathodes ofplatinumor of carbonjor electrolytic purposes but these. materials are notsuitable in the case of electrolytes containing mercuric salts insolution. The reason is that in a mercuric solution platinum quicklybecomes amal gamated and is thereioreuselessior delicate purposes suchas metering. while ,carbon 011 :13116 other hand quickly disintegrates Ihave discovered that eflicient cathodes for use in mercuric solutionsmay bemade from a certain group of substances which for the purposes ofthis j'spe cification I term the iridium group of substances. 'Themembers of this group are iridium, tantalum, niobium, vanadium, silicon(of the form which I may term massive graphitoidal silicon) andmagnetite (either artificial or natural). The substances in this-groupare distinguished from other substances in-the following respects, (a)they are conductorsof electricity; (b) they possess a physical hardnessequal to or exceeding that of iridium; (0) they possess a chemicalinertness equal toor exceeding that of iridium; ('11) they no not amal-;

gamate with mercury in a solution of a mercury salt inthe mercuricstate. V

When iridium is thennember of the group chosen I prefer to employ it initsrolled form or deposited upon glass and either coated or not' withiridium black. When, tantalum, niobium and vanadium ar ei chosen Iprefervto employ them in the io rm 'of foil ,orjpf w'irer When siliconis the substance c'hoseriio'r mycathode I prefer to employ it in theform of what I.nia y term a platinum sandwich that is to say out intothin slices and with two of these slices placed together with a sheet ofplatinum foil placed between them. Any .part' of the platinum which maycome into contact with the electrolyte is covered .by'a' protectivecoating of glass or other suitable material. When magnetite is themember of the group chosen 1 melt it in the elec-.- tric are oroxyhydrogen flame over platinum wire and envelop the latter whereexposed, in glass. Of the substances specified I prefer iridium in theform of rolled sheet and I find that I obtain a great. advantage 'byhardening it by sand blasting before use.

What I claim as my invention and desire to secure by Letters Patent is:-

'1. The combination of an electrolyte containing mercurlc salts insolution, and a cathode of the described iridium gro'up, substantiallyas described.

. 2. The combination of an electrolyte containing mercurlc salts insolution, andscathode characterized by being a conductor ofelectricity,'by possessing a physical hardness and a chemical inertnessat least equal to that of iridium, and by not amalgamating with'mercuryin a solution of a mercury salt in the mercuric state, substantially asdescribed.

In witness whereof I have signed my name to this specification in thepresence of two subscribing witnesses. U HENRY STAFFORD HATFIELD.

Witnesses:

James G. Lonnam,

WILLIAM B. PRINCE.

